Unfortunately, Roux and I haven't developed the relationship between Robert and Rosalind as much as I would like, but we have established some significant details between the two! I really love their relationship, because it's very appropriate for siblings and there's an outward facade of familial irritation, but the pair truly care for each other in a way that transcends most sibling bonds.
In the verse we have set for them, Robert is the older twin, but Rosalind is prone to protecting him and sticking up for him, particularly when they're younger. They argue a considerable amount, too, and Robert is a mama's boy, while Rosalind is daddy's little girl. Rosalind has a deep-rooted resentment towards her mother, as she does in every verse, so this causes the two of them to clash often. However, despite their arguments, Rosalind does what she can to make sure her brother is happy and safe. She would do anything to ensure that, much to Robert's dismay. To some extent, I feel as though he wants to be the one who protects her, not the other way around.